An automotive survey


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A literature survey on automotive embedded systems

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  • How they originated? Engine Control UnitWhat is an Engine Control Unit? Radial enginesElectronic Control Units
  • Memory usually occupies the a lot of space.
  • Power Steering has to do with an ECU that controls a hydraulic pump that pumps hydraulic fluid when, in the direction and as much as the ECU “tells” it to in order to control the steering motion of a car. The ECU knows what has to be done by reading the steering angle on the steering wheel which is the driver input. The ECU reads this input and instructs another set of systems to provide the driver with feedback in the form of steering counterforce on the steering action
  • - The function of the CHI is to implement the FlexRay protocol and it is not dependent on the CPU for this. The communication controller does the job using just information form the CPU.
  • An automotive survey

    1. 1. AN AUTOMOTIVE SURVEY Manu S Ravindra, Colorado State University
    2. 2. AUTOMOTIVE ELECTRONICS • What is it ? Kommandogerat – BMW 801 Radial engine series Radial engine
    3. 3. CONTEMPORARY ECU TRENDS • Around 80 to 100 in a an automobile
    4. 4. ENGINE CONTROL UNIT • A typical modern example
    5. 5. STEER-BY-WIRE (SBW) SYSTEMS – AN EXAMPLE • Power steering
    6. 6. COMMUNICATION BETWEEN ECU‟S • Standard communication protocols are used. CAN (Controller Area Network) LIN (Local Interconnect Network) MOST (Media Oriented Systems Transport) are a few examples.
    7. 7. FLEXRAY – THE FUTURE • A hybrid protocol Time Triggered (TT) messages and Event Triggered (ET) messages • Consists of two segments – Static segment (ST) and Dynamic segment (DYN) • Uses TDMA for communication (Time Division Multiple Access)
    8. 8. SYSTEM MODEL • N1, N2 and N3 are nodes. • Controller Host Interface (CHI) • CPU
    9. 9. SYSTEM ARCHITECTURE • Implemented by two schedulers. • Static Cyclic Scheduler --- non-preempt tasks. --- start time is decided at the design time or “off-line”. • Fixed Priority Scheduler --- preempt tasks. --- scheduled based priorities.
    10. 10. A SCHEDULING EXAMPLE • Τ1 and T6 are SCS scheduled tasks. • The rest of the tasks are FPS tasks.
    12. 12. THE PROTOCOL • Communication occurs in periodic cycles • Each cycle consists of two intervals – ST and DYN intervals • ST and DYN segment lengths can be different but are fixed over the cycles. • Symbol Window and a network idle timer. • Frame Identifier
    13. 13. PAYLOAD SEGMENT • Slot counters – Static and Dynamic • Dynamic mini-slot counters • Node with frame identifier equal to the current slot counter is allowed to communicate.
    14. 14. CLOCK SYNCHRONIZATION • Backbone of FlexRay operation. • Clock system in a distributed system would be subject to “clock-drift”. • Clock drift is an inevitable inherent delay in the arrival of clock from one point to another. • But a global clock reference is needed to keep track of time. • FlexRay uses „micro-ticks” and “macro-ticks”. • “Cluster time” is used as a reference of global clock.
    15. 15. NODE CLOCK CORRECTION • Measure clock delay. • Determine clock correction term. • Apply clock correction term (clock rate correction/clock state correction/both).
    17. 17. WHY FLEXRAY ? FAULT TOLERANCE • Topological Flexibility. • Synchronous Clock. • Conceptual separation.
    18. 18. MODERN ELECTRONIC CONTROL UNITS • Energy was considered to be “freely available” until now. • Energy consumption is directly related to CO 2 emmission of the vehicle. E/E Architecture - Partial networking. - AUTOSAR.
    19. 19. AUTOSAR (AUTOMOTIVE OPEN SYSTEM ARCHITECTURE) • An awesome group of companies working towards delivering the best on production lines to the world! • Similar to the SAE (Society of Automotive Engineers) – Another awesome group. The biggest!
    20. 20. POWER AND ENERGY EFFICIENCY  Optimize energy consumption of electronic components.  Use of networking policies to save power and energy policies. (Communication Energy)
    21. 21. COMMUNICATION ENERGY • Sub-networking. • A “sleep” and “wake-up” object.
    22. 22. CAN – CONTROLLER AREA NETWORK • CSMA – Carrier Sense Multiple Access • Speeds up to 1 Mbps are achievable. • Bus topology. • Nothing specific in the protocol to put a node to sleep / turn-off. • A “sleeping” node “wakes up” if there is any activity on the bus. • CAN sleep object is a random sleep object.
    23. 23. FLEXRAY • TDMA – Time Division Multiple Access. • Speeds up to 10 Mbps are achievable. • Sleep object same as CAN. • Wake up is performed by sending out a specific symbol.
    24. 24. LIN – LOCAL INTERCONNECT NETWORK • Connects sensors and actuators. • One wire communication protocol. • Speeds up to 20kbps. • Master slave network is employed. One way communication. One master controls one or more slaves. Therefore there is no need for conflict avoidance / collision.
    25. 25. MULTI-CORE MCU‟S • Homogeneous and Heterogeneous multi-core MCU‟s. • Multicore benefits. - Redundancy - Monitoring • Code segregation Dedicated use of cores Non-volatile Memory
    26. 26. THANK YOU